Michael Johnson takes a break on a lounge chair in the middle of Broadway in New York's Times Square. Sections of Broadway that run through Times Square and Herald Square have been closed to cars in an effort to reduce traffic and pollution, and cut down on pedestrian accidents. (Seth Wenig/The Associated Press/Seth Wenig/The Associated Press)

Michael Johnson takes a break on a lounge chair in the middle of Broadway in New York's Times Square. Sections of Broadway that run through Times Square and Herald Square have been closed to cars in an effort to reduce traffic and pollution, and cut down on pedestrian accidents.(Seth Wenig/The Associated Press/Seth Wenig/The Associated Press)

'Pop-up' urban planning gives cities the freedom to experiment with projects on a temporary basis, allowing innovative ideas a trial run without expensive commitment of taxpayer money. Cities around the world are embracing the idea, leading in many cases to permanent changes in the urban landscape